Transcript Lecture 27 Human Evolution I

Primates : mammal order with about 185 spp.
(out of 4500 mammal species)
bonnet macaque
squirrel monkey
Primates
- largely tree-dwelling
(arboreal) and tropical
56 mya – opposable toe,
for grasping
Sister order = tree shrews?
(order Scandentia)
Tupaia
MRCA of all primates
lived about 80 mya
CHARACTERISTICS:
 stereoscopic color vision,
bony orbits protect eyes
 large brain relative to
body size
Baboon Hand
 Digits with independent mobility and
opposable thumb
 Flat nails, no claws, sensitive fingers
Prosimians
Loris
(Asian)
 Lemurs
Tarsiers
 Completely
carnivorous
 good leaping
ability
 nocturnal
 southeast
Asia
NEW WORLD MONKEYS
red uakari
pygmy marmoset
OLD WORLD MONKEYS
Proboscis monkey
Hamadryas baboon
 The Hominoidea split from
the Old-world monkeys 2830 MYA
Nature 497, 611–614 (30 May 2013)
Gibbons
Hominoids:
 brachiation
 posture more erect than in
monkeys
 arms and shoulders more
flexible, spine stiffer
 broader, larger pelvis
 loss of a tail
 five-cusp lower molars
instead of four
 scapulae more dorsal so
arms can be extended
laterally
Hominoidea
fraction of total brain
mammals
neocortex
cerebellum
orangutan
"How about this zoo diet!"
Bornean
orangutan
Sumatran
orangutan
human
chimpanzee
gorillla
orangutan
habitual
brachiation
Orangs, genus Pongo
 "old man of the woods"
 fruit eaters, not social, males territorial
 only occasionally on forest floor
 especially endangered in Malaysia
gorilla
Lowland
Mountain
Gorilla - genus Gorilla
 small groups of 10-20
 Dominated by male silverback, male-male
competition - POLYGYNY
 Males almost twice as big as females
Figure 1 Western equatorial Africa. Commercial hunting is concentrated near
transport routes (major roads in white), whereas Ebola impact has been heaviest in
remote areas. Ape density in the Minkébé forest block (shaded area in northern
Gabon) has dropped by about 99% over the past decade. The Ebola epidemic is
currently most severe between Lossi and Odzala National Park. Observations of
unpredated ape carcasses span 600 km, from 40 km west of Booue to the Nouabale–
Ndoki region of northern Congo.
Walsh et al. 2003. NATURE 422:611:614
Genus Pan
chimpanzees
bonobo
chimpanzee
Chimpanzee
Bonobo
Kin groups
Extensive
tool use
Communicating and probing a hidden "snake"
Common chimpanzee
Pan troglodytes
 extended child care,
prolonged adolescence
 puberty at 8-10 years
 feed, sleep in trees, but
often on ground
 polygamous (promiscuity),
highly social
Bonobo - Pan paniscus
Bonobo
Pan paniscus
 much less well known, deep
in rain forests of Congo
 more upright posture, less
"violent" than chimps?
 female bands control
resources; form hierarchy
 male "standing" depends on
its mother's
How are the hominoids related to each other?
The "Line-up"
Gibbon
Orangutan Chimpanzee
Gorilla
Human
millions of
years ago
gibbon
orangutan
gorilla
chimpanzee
human
0
Hominidae
6
Hylobatidae
12
Pongidae
Are gorillas and chimps
each other's closest
relatives?
Only three possibilities:
Go
Ch
Hu
Go
Hu
Ch
WHICH IS CORRECT?
Hu
Ch
Go
% divergence of nucleotides at globin pseudogene
Orang
Pongo
Orang
Gorilla
Gorilla
Gorilla
Chimp
Pan
Human
Homo
3.39
3.42
3.30
1.82
1.70
Chimp
1.56
Human
0.38
Alleles in populations coalesce to a
common ancestor
Incomplete lineage sorting: Gene trees do not
always match species trees
Phylogenetic relationships constructed by
weighing evidence from multiple genes
Data from clock-like genes suggest:
Split between orangs and
chimp-human-gorilla clade
10 - 13 mya
Split between gorillas and
human-chimp clade
8 - 10 mya
Split between human and
chimp from common ancestor
6 - 8 mya